Reliability barrier integration for cu application

ABSTRACT

Embodiments of the present invention provide a process sequence and related hardware for filling a patterned feature on a substrate with a metal, such as copper. The sequence comprises first forming a reliable barrier layer in the patterned feature to prevent diffusion of the metal into the dielectric layer through which the patterned feature is formed. One sequence comprises forming a generally conformal barrier layer over a patterned dielectric, etching the barrier layer at the bottom of the patterned feature, depositing a second barrier layer, and then filling the patterned feature with a metal, such as copper.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 10/841,086, filed May 7, 2004, which is a continuation of U.S.patent application Ser. No. 10/052,681, filed Jan. 17, 2002, now issuedas U.S. Pat. No. 7,026,238, which is a continuation-in-part of U.S.patent application Ser. No. 08/856,116, filed May 14, 1997, which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention relate to a deposition sequence and relatedhardware for manufacturing a plug and line typical of a dual damascenestructure utilizing a thin conformal barrier layer formed on the wallsof the feature.

2. Description of the Related Art

Modern semiconductor integrated circuits usually involve multipleconductive layers separated by dielectric (insulating) layers, such asoxide layers. The conductive layers are electrically interconnected byholes penetrating the intervening oxide layers and contacting someunderlying conductive feature. After the holes are etched, they arefilled with a metal, typically aluminum or copper, to electricallyconnect the conductive layers with each other. In a circuit formed by adual damascene process, there are two types of holes, vias and trenches,which penetrate dielectric layers of the circuit. Vias are holes whichextend to an underlying conductive feature. Vias which are filled with ametal are called plugs, or via plugs. Trenches are holes which extendinto the dielectric layer of the circuit, but do not extend to anunderlying conductive feature. Trenches which are filled with a metalare called lines, which serve as horizontal interconnects in a circuit.

As sizes of features such as holes in integrated circuits continue todecrease, the characteristics of the material forming the plugs becomeincreasingly important. The smaller the plug, the less resistive thematerial forming the plug should be for speed performance. Copper is amaterial which is becoming more important as a result. Copper has aresistivity of 1.7 μΩ-cm. Copper has a small RC time constant therebyincreasing the speed of a device formed thereof. In addition, copperexhibits improved reliability over aluminum in that copper has excellentelectromigration resistance and can drive more current in the lines.

One problem with the use of copper is that copper diffuses into silicondioxide, silicon and other dielectric materials. Therefore, barrierlayers become increasingly important to prevent copper from diffusinginto the dielectric materials and compromising the integrity of thedevice. Barrier materials such as Ta, TaN, SiN, Ti, TiN, W, and WN onthe interlayer dielectric will effectively inhibit interlayer diffusion.However, within the same dielectric layer it is difficult to provide aneffective barrier to prevent leakage between lines. Severaltechnologies, such as physical vapor deposition (PVD), are presentlyunder investigation for adding a barrier layer to the via sidewallseparating the copper metal from the interlayer dielectric. However,common PVD technologies are limited in high aspect structures due to thedirectional nature of their deposition. Thus, the thickness of a barrierlayer deposited by PVD will depend directly upon the structurearchitecture, with the barrier becoming thinner on the sidewall near thestructure bottom. The barrier thickness, and therefore the barrierintegrity may be compromised on the sidewall near the structure bottom.Also, the bottom corners of vias often do not form precise right anglesat their intersection. Instead, there may be recesses or “undercuts” 11at the bottom corners of vias 10 formed in a dielectric layer 12, asshown in FIG. 1. As a result, it is difficult to deposit a barrier layerthat covers these undercuts by PVD because of the limited directionalityof deposition by PVD.

In contrast, chemical vapor deposition (CVD) and atomic layer deposition(ALD) deposited films are, by their nature, conformal in re-entrantstructures. Silicon nitride (Si_(x)N_(y)) and titanium nitride (TiN)prepared by decomposition of an organic material,tetrakis(dimethylamido) titantium (TDMAT) are common semiconductormanufacturing materials which display the described conformalperformance. Both materials are perceived as being good barriers to Cudiffusion, but are considered unattractive due to their highresistivity. The highly resistive nature of these materialsdetrimentally affects the conductivity between the plug and theunderlying conductive features, which must be maintained as low aspossible to maximize logic device performance.

Therefore, there is a need for a process sequence and related hardwarewhich provides a good barrier layer on the via sidewall, but which doesnot negatively affect the conductivity of the plug.

SUMMARY OF THE INVENTION

Embodiments of the present invention generally provide a process andrelated hardware for filling a patterned feature on a substrate withcopper or other conductive materials. One embodiment of the presentinvention comprises forming a generally conformal CVD or ALD barrierlayer over a patterned feature formed in a substrate, etching thebarrier layer at the bottom of the patterned feature, depositing asecond barrier layer that does not significantly impact conductivitybetween the plug and the underlying layer, but provides an adequatebarrier on other surfaces, and then filling the patterned feature with aconductive material, such as copper. Another embodiment of the presentinvention comprises forming a generally conformal CVD or ALD barrierlayer over a patterned feature formed in a substrate having an etchstop, etching the barrier layer and the etch stop at the bottom of thepatterned feature, depositing a second barrier layer, and then fillingthe patterned feature with a conductive material, such as copper.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features of the present invention areattained and can be understood in detail, a more particular descriptionof the invention, briefly summarized above, may be had by reference tothe embodiments thereof which are illustrated in the appended drawings.

It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a partial cross-sectional view of a substrate having undercutsat the bottom of its via, as known in the prior art;

FIGS. 2-8 are partial cross-sectional views of a substrate having oneprocess sequence of the present invention performed thereon;

FIG. 9 is a schematic of a multichamber processing apparatus;

FIG. 10 is a cross-sectional view of a CVD process chamber; and

FIG. 11 is a cross-sectional view of a PVD process chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 2-8 illustrate and describe one embodiment of a process sequenceof the present invention. FIG. 2 is a partial cross sectional view of asubstrate having a via 200 and a trench 202 formed thereon through adielectric layer 204 to an underlying metal layer 206. A conformalbarrier layer 208, shown in FIG. 3, is formed over the patterned surfaceby CVD techniques, such as conventional CVD and rapid CVD, or atomiclayer deposition (ALD). The barrier layer deposited by CVD may be formedfrom materials such as Si_(x)N_(y), TiSi_(x)N, TiN(C), TiNSi(C), Ta,TaC, TaN(C), TaNSi(C), W, WN_(x), SiO_(x)N_(y), SiC, AlN, or Al₂O₃.

While the barrier layer 208 deposited by CVD or ALD provides desiredconformal coverage of a substrate, including the sidewalls 216 and 218of the via and the trench, respectively (FIG. 4), the barrier layer 208also covers the lower portion of the via (FIG. 3), which contacts theunderlying metal layer 206. The barrier layer 208 on the underlyingmetal layer 206 increases the resistance of the overall structure, andnegatively impacts the performance of the structure. Thus, the substrateis exposed to a pre-clean or other etching process, such as anargon/hydrogen etch process to remove a portion of the barrier layerformed on the horizontal surfaces of the patterned feature, i.e, thebottom of the via 210 at the interface with the underlying metal layer206, the bottom of the trench 212, and the field surface 214, as shownin FIG. 4. The etching may also extend into and remove part of theunderlying metal layer (not shown). Preferably, the etching process isperformed within a system that also includes the chamber in which thebarrier layer 208 is deposited by chemical vapor deposition, so that thesubstrate is not exposed to air. More preferably, the etching process isperformed within the same chamber in which chemical vapor deposition ofthe barrier layer is performed. However, in another embodiment, there isan air break in which the substrate is moved out of the processingsystem after the deposition of the barrier layer 208 and before theetching process.

Removing the barrier layer 208 from the bottom of the via 210 ensures agood, low resistance electrical contact to the underlying metal layer206. However, removing the barrier layer 208 from another surface of thepatterned feature, i.e., the bottom of the trench 212, leaves thedielectric layer 204 exposed at the bottom of the trench 212.

In the present invention, following the etch process, a second barrierlayer 220, such as Ta, TaN, TiSiN_(x), TaSiN_(x), W, or WN_(x) issputter deposited using PVD onto the first barrier layer 208 and theexposed dielectric layer at the bottom of the trench 212, as shown inFIG. 5. The PVD barrier layer 220 covers the bottom of the trench 212and the field surface 214. The PVD barrier layer 220 on the bottom ofthe trench 212 covers the dielectric layer at the bottom of the trenchwhich was previously exposed during the etching process to remove thebarrier layer 208 from the bottom of the via 210. The PVD barrier layer220 may also partially or completely cover the vertical surfaces of thepatterned feature, such as the sidewalls 216, 218 of the trench 202 andthe via 200, respectively. However, the deposition of the PVD barrierlayer 220 is minimized at the bottom of the via 210. At this point inthe process, the aspect ratio of the via will typically be in the rangeof about 4 to 1, and the aspect ratio of the trench will typically be inthe range of about 1 to 1. Because of the high aspect ratio/narrowopening of the via 200, few of the atoms or molecules sputtered by PVDwill be sputtered at the appropriate angle to reach the bottom of thevia 210. High density plasma PVD (HDP-PVD) or other directional PVDtechniques may be used to further minimize deposition on the bottom ofthe via.

In another embodiment, the second barrier layer is deposited, at leastpartially, at the bottom of the via (not shown). For example, thebarrier layer may have a thickness of from about 20 Å to about 50 Å atthe bottom of the via. Preferably, the PVD barrier layer covering thebottom of the via has a low resistance. Examples of barrier layers witha low resistance, e.g., less than about 250 μΩ-cm, include PVD Ta, TaN,W, WN_(x), Ti, and TiN layers. Preferably, the second barrier layerdeposited by physical vapor deposition is sufficient to provide abarrier on the bottom of the trench without significantly impairingconduction between the conductive material that is deposited later inthe via and the underlying metal layer.

A copper seed layer 222 is then deposited on the patterned substrate bya PVD, CVD, or electroless deposition, as shown in FIG. 6. A seed layeris a layer on which a subsequent metal layer can be deposited by aprocess such as PVD, CVD, or electroplating. Copper is deposited on theseed layer by PVD, CVD, or electroplating to fill the trench and viafeatures on the patterned substrate (not shown).

A similar process sequence may be performed on a patterned substratewith an etch stop, such as a nitride etch stop, at the via level. FIG. 7shows the starting material patterned substrate with an etch stop 224disposed at the bottom of the feature. The steps of a preferredembodiment of this method are illustrated by FIGS. 2, 3, 8, and 5. FIG.8 shows that the etch stop 224 is removed from the bottom of the via 210during the etching step which removes the barrier layer 208 from thebottom of the via 210.

A schematic of a multichamber processing apparatus 35 suitable forperforming the processes of the present invention is illustrated in FIG.9. The apparatus is an “ENDURA” system commercially available fromApplied Materials, Santa Clara, Calif. The particular embodiment of theapparatus 35 shown herein is suitable for processing planar substrates,such as semiconductor substrates, and is provided to illustrate theinvention, and should not be used to limit the scope of the invention.The apparatus 35 typically comprises a cluster of interconnected processchambers 36, for example, CVD and PVD deposition and rapid thermalannealing chambers.

The apparatus comprises a CVD deposition chamber 41 (shown in FIG. 10)which is used to deposit the conformal barrier layer 208 in oneembodiment. The CVD deposition chamber 41 has surrounding sidewalls 45and a ceiling 50. The chamber 41 comprises a process gas distributor 55for delivering process gases into the chamber. Mass flow controllers andair operated valves are used to control the flow of process gases intothe deposition chamber 41. The gas distributor 55 is typically mountedabove the substrate (as shown), or peripherally about the substrate (notshown). A support 65 is provided for supporting the substrate in thedeposition chamber 41. The substrate is introduced into the chamber 41through a substrate loading inlet in the sidewall 45 of the chamber 41and placed on the support 65. The support 65 can be lifted or lowered bysupport lift bellows 70 so that the gap between the substrate and gasdistributor 55 can be adjusted. A lift finger assembly 75 comprisinglift fingers that are inserted through holes in the support 65 can beused to lift and lower the substrate onto the support to facilitatetransport of the substrate into and out of the chamber 41. A thermalheater 80 is then provided in the chamber to rapidly heat the substrate.Rapid heating and cooling of the substrate is preferred to increaseprocessing throughput, and to allow rapid cycling between successiveprocesses operated at different temperatures. The temperature of thesubstrate is generally estimated from the temperature of the support 65.

The substrate is processed in a process zone 95 above a horizontalperforated barrier plate 105. The barrier plate 105 has exhaust holes110 which are in fluid communication with an exhaust system 115 forexhausting spent process gases from the chamber 41. A typical exhaustsystem 115 comprises a rotary vane vacuum pump (not shown) capable ofachieving a minimum vacuum of about 10 mTorr, and optionally a scrubbersystem for scrubbing byproduct gases. The pressure in the chamber 41 issensed at the side of the substrate and is controlled by adjusting athrottle valve in the exhaust system 115.

A plasma generator 116 is provided for generating a plasma in theprocess zone 95 of the chamber 40 for plasma enhanced chemical vapordeposition processes. The plasma generator 116 can generate a plasma (i)inductively by applying an RF current to an inductor coil encircling thedeposition chamber (not shown), (ii) capacitively by applying an RFcurrent to process electrodes in the chamber, or (iii) both inductivelyand capacitively while the chamber wall or other electrode is grounded.A DC or RF current at a power level of from about 750 Watts to about2000 Watts can be applied to an inductor coil (not shown) to inductivelycouple energy into the deposition chamber to generate a plasma in theprocess zone 95. When an RF current is used, the frequency of the RFcurrent is typically from about 400 KHz to about 16 MHZ, and moretypically about 13.56 MHZ Optionally, a gas containment or plasma focusring (not shown), typically made of aluminum oxide or quartz, can beused to contain the flow of process gas or plasma around the substrate.

In another embodiment, a conformal barrier layer 208 is formed over thepatterned surface by atomic layer deposition (ALD). The ALD barrierlayer may be formed from materials such as Ta, TaN, W, or WN. Examplesof ALD processes are described in commonly assigned U.S. patentapplication Ser. No. 09/754,230, entitled “Method of Forming RefractoryMetal Nitride Layers Using Chemisorption Techniques,” filed on Jan. 3,2001, U.S. patent application Ser. No. 09/960,469, entitled “Formationof Refractory Metal Nitrides Using Chemisorption Techniques,” filed onSep. 19, 2001, and U.S. patent application Ser. No. 09/965,370, entitled“Integration of Barrier Layer and Seed Layer,” filed on Sep. 26, 2001,which are hereby incorporated by reference.

Generally, ALD can be used to deposit monolayers of materials, such asmonolayers of a nitrogen-based compound and a metal containing compound,which are alternately chemisorbed on a substrate. For example, amonolayer of a nitrogen-based compound is chemisorbed on a substrate byintroducing a pulse of a nitrogen-based gas into a processing chamber.After the monolayer is chemisorbed onto the substrate, excessnitrogen-based compound is removed from the processing chamber byintroducing a pulse of purge gas thereto. Purge gases, such as, forexample, helium (He), argon (Ar), nitrogen (N₂), and hydrogen (H₂), andother gases, may be used. After the pulse of purge gas, a pulse of ametal containing compound is introduced into the processing chamber tochemisorb a monolayer of metal containing compound on the substrate. Themetal containing compound may be provided as a gas or may be providedwith the aid of a carrier gas. Examples of carrier gases which may beused include, but are not limited to, helium (He), argon (Ar), nitrogen(N₂), and hydrogen (H₂).

In another embodiment of ALD, instead of using pulses of a purge gasbetween the pulses of a nitrogen-based compound and a metal containingcompound, the purge gas is continuously flowed, i.e., both during thepulses of a nitrogen-based compound and the pulses of a metal containingcompound, and in between these pulses.

One exemplary process of depositing a tantalum nitride barrier layer byatomic layer deposition in a processing chamber comprises sequentiallyproviding pentadimethylamino-tantalum (PDMAT) at a flow rate betweenabout 100 sccm and about 1000 sccm, and preferably between about 200sccm (standard cubic centimeters per minute) and 500 sccm, for a timeperiod of about 1.0 second or less, providing ammonia at a flow ratebetween about 100 sccm and about 1000 sccm, preferably between about 200sccm and 500 sccm, for a time period of about 1.0 second or less, and apurge gas at a flow rate between about 100 sccm and about 1000 sccm,preferably between about 200 sccm and 500 sccm for a time period ofabout 1.0 second or less. The heater temperature preferably ismaintained between about 100° C. and about 300° C. at a chamber pressurebetween about 1.0 and about 5.0 torr. This process provides a tantalumnitride layer in a thickness between about 0.5 Å and about 1.0 Å percycle. The alternating sequence may be repeated until a desiredthickness is achieved.

A pre-clean chamber which can be used to remove the barrier layer 208from the bottom of the via 210 is the Pre-Clean II chamber availablefrom Applied Materials, Inc. of Santa Clara, Calif. Additionally, otheretch chambers known in the field could be used to remove the barrierlayer as described. In a preferred embodiment, the CVD chamber 41 ofFIG. 16 can be used to etch the CVD barrier layer deposited on thesubstrate. The support pedestal 82 may be used to bias the substrate. Aplasma generator 116, as described above, is attached to the supportpedestal 82. Argon is the principal etching gas. It ionizes in thechamber, and its positively charged ions are attracted to the negativelybiased substrate with enough energy that the barrier layer 208 isremoved from the horizontal surfaces of the patterned feature.

In another embodiment, the barrier layer 208 may be deposited and thenremoved from the bottom of the via 210 in an ALD chamber with plasmacapability.

A conventional PVD deposition chamber commercially available fromApplied Materials, Santa Clara, Calif. can be used to deposit a secondbarrier layer 220 on a substrate. FIG. 11 shows a simplified example ofa PVD chamber 300. The PVD chamber 300 generally includes a chambersection 306. The chamber section 306 generally includes a substratesupport member 302 for supporting a substrate (not shown) to beprocessed, a target 304 for providing a material to be deposited on thesubstrate and a process environment 303 wherein a plasma is created forions to sputter the target 304.

The PVD chamber 300 generally includes the substrate support member 302,also known as a susceptor or heater, disposed within the chamber section306. The substrate support member 302 may heat the substrate if requiredby the process being performed. A target 304 is disposed in the top ofthe chamber section 306 to provide material, such as aluminum, titaniumor tungsten, to be sputtered onto the substrate during processing by thePVD chamber 300. A lift mechanism, including a guide rod 326, a bellows328 and a lift actuator 330 mounted to the bottom of the chamber section306, raises the substrate support member 302 to the target 304 for thePVD chamber 300 to perform the process and lowers the substrate supportmember 302 to exchange substrates. A set of shields 332, 334, 336,disposed within the chamber section 306, surround the substrate supportmember 302 and the substrate during processing in order to prevent thetarget material from depositing on the edge of the substrate and onother surfaces inside the chamber section 306.

Situated above the chamber section 306 and sealed from the processingregion of the chamber is a cooling chamber 316. The cooling chamber 316is generally defined by the target 304, a top 317 and sides 319. Acooling fluid, such as water or antifreeze, flows into the coolingchamber 316 through inlet 318 and out of the cooling chamber 316 throughoutlet 320.

A rotating magnetron 308 is disposed in the cooling chamber 316 on thenon-process environment side of the target 304 and surrounded by thecooling fluid. The magnetron 308 is isolated from the vacuum in thechamber section 306 by seals (not shown) between the magnetron chamberand target and between the target and processing region. The magnetron308 has a set of magnets 310 arranged within the magnetron 308 so thatthey create magnetic field lines spinning across the sputtering surfaceof the target. Electrons are captured along these lines, where theycollide with gas atoms, creating ions. To create this effect about thecircumference of the target, the target is rotated during processing.The magnetron 308 is situated above the top side of the target 304 withabout a one millimeter gap therebetween, so the magnetic fields from themagnets 310 may penetrate through the target 304. A motor assembly 312for rotating the magnetron 308 is mounted to the top 317 of the coolingchamber 316. A shaft 314, which mechanically couples the motor assembly312 to the rotational center of the magnetron 308, extends through thetop 317. The motor assembly 312 imparts a rotational motion to themagnetron 308 to cause it to spin during performance of the substrateprocess.

A negative DC bias voltage of about 200 V or more is typically appliedto the target 304, and a ground is applied to an anode, the substratesupport member 302, and the chamber surfaces. The combined action of thedc bias and the rotating magnetron 308 generate an ionized plasmadischarge in a process gas, such as argon, between the target 304 andthe substrate. The positively charged ions are attracted to the target304 and strike the target 304 with sufficient energy to dislodge atomsof the target material, which sputters onto the substrate.

The process can be implemented using a computer program product thatruns on a conventional computer system comprising a central processorunit (CPU) interconnected to a memory system with peripheral controlcomponents, such as for example a 68400 microprocessor, commerciallyavailable from Synenergy Microsystems, California.

EXAMPLE 1

In one example, a process according to the present invention wasperformed on a substrate having a 0.25 μm via with about a 4:1 aspectratio and a trench. The patterned substrate was first introduced into aCVD chamber, such as a TxZ® chamber, commercially available from AppliedMaterials, Inc., Santa Clara, Calif., where about 50 Å to about 100 Å ofSi_(x)N_(y) was deposited on the substrate using CVD techniques. Thesubstrate was then moved into a Pre-clean II chamber (available fromApplied Materials, Inc., located in Santa Clara, Calif.), where thesubstrate was subjected to an argon/hydrogen etching environment forabout 20 seconds. RF/DC powers of about 300/300 W were used. Next, thesubstrate was moved into a PVD chamber where about 400 Å of TaN wasdeposited on the substrate in the field. Next, the substrate wasintroduced into a CVD chamber where about 400 Å of CVD Cu was depositedon the substrate as a wetting layer. Then, Cu was sputtered onto thesubstrate to complete the fill the via and the trench.

EXAMPLE 2

In another example, a patterned substrate with a dual damascene trenchstructure and a via opened to an underlying Cu wiring was firstintroduced into a multichamber processing apparatus having a sputterclean chamber, a CVD barrier chamber, a PVD barrier chamber, and a PVDCu chamber. 50 Å of TiSi_(x)N was deposited on the substrate in a CVDbarrier chamber at a pressure of less than 10 Torr and at a temperatureof about 300° C. to about 380° C. by reacting TDMAT in a N₂/H₂environment to form a plasma. The substrate was then treated with a SiH₄soak. The deposited TiSi_(x)N conformally covered both the via andtrench structure. In the next step, the substrate was moved to thesputter clean chamber, and subjected to argon/hydrogen etch to etch offthe TiSi_(x)N film deposited at the bottom of the via. The etching wascontinued past the bottom of the via into the underlying Cu wiring toremove about 5 to 10 Å of the underlying Cu wiring. The etch processalso removed the TiSi_(x)N film at the bottom of the trench structure.Next, the substrate was moved into a PVD Ta/TaN chamber to receive aTa/TaN film having a thickness at the bottom of the trench structure ofabout 30 Å. Then, the substrate was transferred into a PVD Cu chamberwhere about 1500 Å of Cu was deposited on the substrate with minimaldeposition at the bottom of the via.

While the foregoing is directed to the preferred embodiment of thepresent invention, other and further embodiments of the invention may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims which follow.

1. A method of forming a barrier on a substrate having a recessedfeature formed therein, the method comprising: depositing a nitridebarrier layer on the substrate; etching through the nitride barrierlayer so as to expose at least a bottom portion of the recessed feature;depositing an additional nitride barrier layer on the substrate; anddepositing a copper pre-layer on the substrate.
 2. The method of claim1, further comprising depositing copper on the copper pre-layer.
 3. Themethod of claim 2, wherein the depositing copper on the copper pre-layercomprises electroplating copper.
 4. The method of claim 1, wherein thedeposition of the additional nitride barrier layer is performed in thepresence of a high density plasma.
 5. The method of claim 1, wherein theadditional nitride barrier layer is a TaN layer.
 6. The method of claim1, wherein the depositing a nitride barrier layer comprises a vapordeposition.
 7. A method of forming a barrier on a substrate having arecessed feature formed therein, the method comprising: depositing anitride barrier layer on the substrate; etching through the nitridebarrier layer so as to expose at least a bottom portion of the recessedfeature; depositing an additional nitride barrier layer on thesubstrate, wherein the additional nitride barrier layer covers thebottom of the recessed feature; and depositing a copper layer on thesubstrate.
 8. The method of claim 7, further comprising electroplatingcopper on the copper layer.
 9. The method of claim 8, wherein theelectroplating copper on the copper layer fills the recessed feature.10. The method of claim 7, wherein the deposition of the additionalnitride barrier layer is performed in the presence of a high densityplasma.
 11. The method of claim 7, wherein the additional nitridebarrier layer is a TaN layer.
 12. The method of claim 7, wherein thedepositing a nitride barrier layer comprises a vapor deposition.
 13. Amethod of forming a barrier on a substrate having a recessed featureformed therein, the method comprising: depositing a nitride barrierlayer on the substrate, wherein the nitride barrier layer covers thebottom of the recessed feature, and wherein the depositing a nitridebarrier layer comprises etching barrier material from the bottom of therecessed feature after deposition of the barrier material; and thendepositing a copper pre-layer on the substrate.
 14. The method of claim13, wherein etching barrier material from the bottom of the recessedfeature exposes the bottom of the recessed feature.
 15. The method ofclaim 13, further comprising depositing copper on the copper pre-layer.16. The method of claim 15, wherein the depositing copper on the copperpre-layer comprises electroplating copper.
 17. The method of claim 15,wherein depositing copper on the copper pre-layer fills the recessedfeature.
 18. The method of claim 13, wherein the deposition of thenitride barrier layer is performed in the presence of a high densityplasma.
 19. The method of claim 13, wherein the nitride barrier layercomprises tantalum nitride.
 20. The method of claim 13, where thedepositing a nitride barrier layer comprises a vapor deposition.
 21. Amethod of forming a barrier on a substrate having a recessed featureformed therein, the method comprising: depositing a nitride barrierlayer on the substrate; etching through the nitride barrier layer so asto expose at least a bottom portion of the recessed feature; sputteringadditional barrier material from a target onto the substrate; anddepositing a copper pre-layer on the substrate.
 22. The method of claim21, wherein sputtering additional barrier material from a target ontothe substrate comprises depositing an additional barrier layer on thesubstrate.
 23. The method of claim 22, wherein the additional barrierlayer is a TaN layer.
 24. The method of claim 21, wherein the additionalbarrier material comprises tantalum.
 25. The method of claim 21, furthercomprising depositing copper on the copper pre-layer to fill therecessed feature.
 26. The method of claim 25, wherein the depositingcopper on the copper pre-layer comprises electroplating copper.
 27. Themethod of claim 21, wherein the sputtering comprises a high densityplasma process.